Dorsomedial prefrontal cortex neurons encode nicotine-cue associations

The role of medial prefrontal cortex (mPFC) in regulating nicotine taking and seeking remains largely unexplored. In this study we took advantage of the high time-resolution of optogenetic intervention by decreasing (Arch3.0) or increasing (ChR2) the activity of neurons in the dorsal and ventral mPFC during 5-s nicotine cue presentations in order to evaluate their contribution to cued nicotine seeking and taking. Wistar rats were trained to self-administer intravenous nicotine in 1 h self-administration sessions twice a day for a minimum of 10 days. Subsequently, dmPFC or vmPFC neuronal activity was modulated during or following presentation of the 5-s nicotine cue, both under extinction and self-administration conditions. We also used in vivo electrophysiology to record the activity of dmPFC neurons during nicotine self-administration and extinction tests. We show that optogenetic inhibition of dmPFC neurons during, but not following, response-contingent presentations of the nicotine cue increased nicotine seeking. We found no effect on nicotine self-administration or on food seeking in an extinction test. We also show that this effect is specific to dmPFC, because optogenetic inhibition of vmPFC had no effect on nicotine seeking and taking. In vivo recordings revealed that dmPFC network neuronal activity was modulated more strongly following nicotine cue presentation in extinction, compared to following nicotine self-administration. Our results strongly suggest that a population of neurons within the dmPFC is involved in encoding the incentive value of nicotine-associated cues.

Examination of the effects of cannabinoid ligands on decision making in a rat gambling task

Although exposure to delta-9-tetrahydrocannabinol (THC) is perceived to be relatively harmless, mounting evidence has begun to show that it is associated with a variety of cognitive deficits, including poor decision making. THC-induced impairments in decision making are thought to be the result of cannabinoid CB1 receptor activation, and although clinical literature suggests that chronic activation via THC contributes to perturbations in decision making, acute CB1 receptor modulation has yielded mixed results. Using an animal model to examine how CB1-specific ligands impact choice biases would provide significant insight as to how recruitment of the endocannabinoid system may influence decision making. Here, we used the rat gambling task (rGT), a validated analogue of the human Iowa Gambling Task, to assess baseline decision making preferences in male Wistar rats. After acquisition rGT performance was measured. Animals were challenged with the CB1 receptor antagonist rimonabant, the partial agonist THC, and the synthetic agonist WIN55,212-2. Animals were also treated acutely with the fatty acid amide hydrolase (FAAH) inhibitor URB597 to selectively upregulate the endocannabinoid anandamide. Blockade of the CB1 receptor produced a trend improvement in decision making in animals who preferred the advantageous task options, yet left choice unaffected in risk-prone rats. Neither CB1 receptor agonist had strong effects on decision making, but a high dose THC decreased premature responses, whereas WIN55,212-2 did the opposite. URB597 did not affect task performance. These results indicate that although chronic CB1 receptor activation may be associated with impaired decision making, acute modulation has modest effects on choice and instead may play a substantive role in regulating impulsive responding.

Salmonella rarely detected in Mississippi coastal waters and sediment

AIMS

Standards for the rapid detection of individual pathogens from environmental samples have not been developed, but in their absence, the use of molecular-based detection methods coupled with traditional microbiology techniques allows for rapid and accurate pathogen detection from environmental waters and sediment. The aim of this research was to combine the use of enrichment with PCR for detection of Salmonella in Mississippi coastal waters and sediment and observe if that presence correlated with levels of enterococci and climatological variables.

METHODS AND RESULTS

Salmonella were primarily found in samples that underwent nutrient enrichment and were present more frequently in freshwater than marine waters. Salmonella were detected infrequently in marine and freshwater sediments. There was a significant positive correlation between the presence of detectable Salmonella and the average enterococcal count. An inverse relationship, however, was observed between the frequency of detection and the levels of salinity, turbidity and sunlight exposure.

CONCLUSIONS

Results from this study indicated the presence of Salmonella in Mississippi coastal waters, and sediments are very low with significant differences between freshwater and marine environments.

SIGNIFICANCE AND IMPACT OF THE STUDY

Using pathogenic and novel nonpathogenic molecular markers, Salmonella do not appear to be a significant pathogenic genus along the Mississippi Coast.

Gentamicin dosing requirements in patients with acute pancreatitis

Increased endothelial permeability is postulated in patients with pancreatic inflammatory disease. As a result, a deficit in total circulating blood volume may occur as fluid is sequestered within the extravascular space. To counteract this fluid sequestration, exogenous fluid is administered, which results in expansion of total body water. The object of this study was to determine whether the fluid sequestration and potential total body water increase observed in patients with the diagnosis of pancreatitis affects the pharmacokinetics--and thus dosing requirements--of the water-soluble aminoglycoside gentamicin. Data collected from a clinical pharmacokinetic monitoring service were analyzed in 17 patients with primary diagnoses of acute pancreatitis and 17 closely matched controls. Volume of distribution corrected for total body weight (p = 0.029), volume of distribution corrected for ideal body weight (p = 0.031), and total body gentamicin clearance (p = 0.05) were determined to differ statistically in pancreatitis patients from those values calculated in control patients. Patients with pancreatic inflammatory disease, on the basis of these pharmacokinetic parameter estimates, were found to require approximately a 25% greater dose than controls in order to achieve therapeutic peak serum gentamicin concentrations.

Graphite Furnace Atomic Absorption Spectrophotometric Determination of 4-Hydroxy-3-Nitrobenzene Arsonic Acid in Finished Animal Feed: Collaborative Study

Eight laboratories participated in a collaborative study of an atomic absorption spectrophotometric (AAS) method for determination of 4- hydroxy-3-nitrobenzene arsonic acid (roxarsone), which is administered in animal feed at levels of 25-50 ppm as a growth stimulant. The drug is extracted from feed by using aqueous 1% ammonium carbonate solution. Undissolved feed particles are allowed to settle, and then a diluted aliquot of the feed extract is analyzed for total arsenic by AAS using a graphite furnace for sample atomization. Collaborators performed single analyses on 18 samples which were randomly numbered blind duplicate pairs of a complete poultry ration fortified with roxarsone at concentrations from 22.5 to 55.0 ppm. Statistical evaluation of the collaborative data showed satisfactory method performance. Overall mean recovery of roxarsone was 100.4% and the overall relative standard deviation was 6.2%. The method has been adopted official first action.